Capacitative commutator



25, 1954 N. D. NEWBY 2,679,551

CAPACITATIVE COMMUTATOR Filed Sept. 21, 1950 2 Sheets-Sheet 1 IA IVENTORBy M 0. NEW?! ATTORNEY Patented May 25, 1954 UETED STATES PATENT OFFICECAPACITATIVE COMMUTATOR Neal D. Newby, Leonia, N. J., assignor to BellTelephone Laboratories, Incorporated, New York, N. Y., a corporation ofNew York Application September 21, 1950, Serial No. 185,929

20 Claims. 1

In accordance with the present invention an improved and simplifiedscanning arrangement is provided comprising an electrostatic scanningdevice or distributor which is employed to scan each of the callinglines and supply the necessary pulses for recording the electricalconditions of each of the lines magnetically. In the exemplaryembodiment set forth herein the magnetic material employed for recordingand storing signals comprises a surface layer upon a rotating drum.However, any suitably moving surface layer of magnetic material such asa disc, belt, etc., which moves in a closed or reentrant path may beemployed equally well in combination with the circuits and otherapparatus embodying this invention.

In accordance with the present invention the electrostatic distributoror scanning device is riven from the same shaft as the magnetic drum orfrom the same source of power thus greatly simplifying or eliminatingthe necessity of :t.

synchronizing the rotation of the magnetic drum and a time divisionscanning mechanism such as the electron beam of the cathode-ray tube setforth in the above-identified application of et a1.

Features of this invention relate to shielding of the various conductorsso that the electrical condition of the various lines may be accuratelydetermined.

Other features of the invention relate to controlling the voltage orpotential of certain shield-' ed conductors in accordance with thevoltage obtained from the distributor thus further improving thereliability of operation of the scanning mec.-anism.

Another feature of the invention relates to a scanning mechanism whichdoes not require appreciable power to b supplied to it from the linesand thus does not induce any interference in the lines to which it isconnected.

Another feature of this invention relates to an electrostaticdistributing mechanism in which the connections to the rotatingmechanism are by means of electrostatic elements thus avoiding allresistive and frictional contacts, which contacts are frequently thesource of noise and other spurious signals which interfere with thereliability of determining the electrical condition of each of thecalling lines connected thereto.

The foregoing and other objects and features of this invention may bemore readily understood from the following description of an exemplaryembodiment thereof when read with reference to the attached drawing inwhich:

Fig. 1 shows a simplified embodiment; and

Fig. 2 shows in detail the amplifier circuits required to record andrespond to the recorded signals.

Fig. 1 shows the electrostatic scanner of a type suitable for use incombination with the magnetic drum for recording calling signals such asencountered in telephone switching systems and other callingarrangements. As shown in the exemplary embodiment described herein indetail, the scanner is mounted on the same shaft as the rotatingmagnetic drum. However, when desired this scanning mechanism may bedriven from some other shaft which may be geared to the magnetic drumdriving means or otherwise synchronized with the drum driving means.

The scanning device, as shown in the upper left-hand portion of Fig. 1,comprises a rotating conductive arm 25 insulatively mounted on shaft I00which is the same shaft employed to rotate drum NM. The end 21 of therotating arm 25 passes adjacent to but does not touch or make contactwith a plurality of segments 32, 33, etc. This arm in approaching eachsegment forms a condenser with the segment and has a voltage or currentinduced on or in it in accordance with the voltage of the segment. Therotating arm 25 is surrounded by a shield 26 which rotates but isinsulatively supported therefrom. The rotating element 25 is likewiseinsulatively supported from the shaft. A pair of stationary rings 23 and24 are provided. The ring 23 is electrostatically coupled to therotating member 25 of the scanning or distributing mechanism andstationary ring 24 is capacitatively coupled to the shielding member 26.As shown in the drawings the capacitative elements 23 and 24 are in theform of rings placed in close proximity to the respective rotatingelements of the distributor or scanning mechanism with which they cooperate to form an electric circuit. It is to be understood, of course,that any suitable form of electrostatic capacitative coupling may beemployed or that any other suitable type of coupling may be employedincluding brushes resting on slip rings. However, the capacita-tivecoupling is employed in. the present embodiment of this inventionbecause it is particularly well adapted for coupling to the rotatingelements which in turn are capacitatively coupled to the segments 32,33, etc., because this form of coupling intro duces substantially noextraneous signals, noise currents or other interfering or straycurrents, which currents would interfere with the low level signalspicked up by the rotating member 25 as will be described hereinafter. Inorder to prevent excessive voltage drop across this coupling capacity,it is desirable that its capacity be large compared to the capacitybetween the rotating arm 25 and the segments which it passes.

The segments 32, 33, etc., of the distributor are separated by shieldedsegments which are connected to ground or battery as shown in thedrawing. These segments are provided to prevent interference between thevarious adjacent segments assigned to the individual lines as will bedescribed hereinafter and also to improve the response or outputobtained from the rotating arm 25.

The shielded member 26 is provided together with the shielded cable fromthe stationary rings 23 and 24 to prevent stray voltages induced fromother sources from interfering with signals picked up by the rotatingarm 25.

In an exemplary embodiment of the invention the recorder consists of amagnetic drum, the magnetic surface of which is provided with sufficientarea to be employed in common by 1000 subscribers lines, each linehaving reserved for its use an arc of about .36 degree. The lineelectrodes of the capacitative scanner for such an exemplary embodimentmay be arranged on a flat plate perpendicular to the shaft or they maybe arranged on the inner surface of a ring as shown on the drawing, theline electrodes also being spaced .36 degree. The scanning electrode 25is mounted on the shaft of the drum and its associated amplifiers 2| andiii are employed to amplify the received signals sufliciently to actuatethe magnetic recording equipment.

As the scanning electrode 25 passes each line electrode such as 32, 33,etc., the electrical condition of the line may be recorded in the spaceon the magnetic drum reserved for it.

The sampling rate, that is, the speed of rotation of the scanningelectrode must be sufficiently high to recognize the significantcharacteristics of the pulses or other received signals which are to berecorded. Assuming that the signals received are in the form of dialpulses, then the speed of rotation of the magnetic drum and also thescanning electrode 25 must be such that this electrode makes onecomplete revolution for each open interval of the dial and anothercomplete revolution for each closed interval of the dial. When desired,the scanning electrode may make more than one revolution during each ofthese intervals and the system will operate the same as describedhereinafter.

Inasmuch as the scanner rotates at a relatively high speed and inasmuchas the segments 32, 33, etc., are of relatively small dimensionsmeasured in degrees of arc, the scanning circuit together with itsamplifier and other related equipment must be designed to respond topulses of relatively short duration and therefore must be arranged anddesigned to respond to high frequency currents. If the calling orsubscribers lines are subject to these high frequency currents, it willbe raole and sometimes necessary to provide suitable filtering elementsbetween the line circuit and the electrostatic scanner.

As shown in the drawing each line segment individual to a calling lineis connected to a resistor through which the line current of that lineflows. Consequently, the voltage drop across this resistor is thevoltage applied to the capacitative scanner elements and this voltagecauses the signals to be induced in the rotating element 25 as will bedescribed hereinafter.

Another element of the present recording mechanism comprises a magneticstorage device. in the exemplary embodiment of this invention set forthherein the magnetic material employed for recording and storing signalscomprises a layer upon a rotating drum. However, any suitably movinglayer or surface of magnetic material such as a disc, belt, etc., whichmoves in a closed or reentrant path may be employed equally well incombination with the circuits and other apparatus embodying thisinvention.

The drum employed in the exemplary embodiment set forth herein in detailmay be constructed of suitable structural material as, for example,brass, bronze tubing, stainless steel tubing, aluminum tubing, iron orsteel tubing or any other suitable type of structural. materialincluding plastic materials and other insulating materials, the purposeof the structural material being to provide a cylindrical surface whichmay be retated about its axis by driving means of suitable type such asan electric motor. The drum may be driven directly by or by means ofgears, belts or any other form of mechanical connection, and the motorsenergized from a suitable source of power, including batteries or othermeans. The speed of the motor is not critical and need not be maintainedin synchronism with any other apparatus, so long as it rotates the shaft00 and thus the drum I04 and the capacitative collector or distributoror scanning element 25 at the same speed and in synchronism with eachother and sufiiciently fast to provide one sampling interval for eachline during each of the shortest signaling conditions on the line whichit is desired to recognize.

The surface of the drum is accurately true running and is provided witha layer of magnetic material which an exemplary embodiment employingmetallic drums may take the form of an electroplated coating of magneticmaterial, such as a nickel-cobalt alloy or the like which has athickness in the range from approximately .0003 inch to approximately.0006 inch.

A plurality of recording and pick-up coils comprising one or morewindings on a ferromagnetic core structure are mounted. in closeproximity to the plated surface but not in contact with it. It will beconvenient hereafter to speak of the recording process as writing. Thesignals to be written or recorded are of a pulse-like charactor and haveone or the other of two different values or characteristics, one beingcalled X signals and the other 0 signals. The recording coils and thepick-up coils comprise a core structure having pole tips brought closetogether and placed in close proximity to the magnetic surface of thedrum. Coils are wound on each 01 these cores and when employed forrecording 0: writing the coil is employed to produce a mag netic fluxacross the pole tips which alters th magnetic condition of the surfaceof the drum. In the pick-up coils the magnetic condition of the druminduces a fiux change between the polepieces and thus within the corestructure of the pick-up coil. Consequently, a winding surrounding thesecores has a voltage induced in it in accordance with the magneticcondition of the drum.

The circumferential area of the drum which passes immediately beneaththe pole tips of a given coil or head is defined as a channel and thatpart of the channel which is directly under or immediately adjacent topole tips of a given coil when a pulse of recording or writing currentis applied to the coil is known as a cell or elemental area of thechannel and is assigned to a given line. In the case of a multiplicityof recording coils or writing heads and a multiplicity of pick-up coilsor reading heads, the aggregate of the elemental areas or cells whichare under the several coils at any one instant of time is defined as aslot and is assigned to a given line. The group of cells or elementalareas assigned to a calling line pass under the respective coils atsubstantially the instant of time that the scanning electrode 25 ispassing over the segment of the electrostatic distributor assigned tothe same line. The simplest arrangement of such a slot is a rectangulararea running parallel with the axis on the surface of the drum. It is tobe understood, however, that in the usual case this slot will be more ofa complicated form and is not therefore limited to such a rectangulararea. When the various pick-up coils or recording coils or heads arestaggered or arranged in the form of a spiral or helix around the drumthe slot may be helical or may have a saw-tooth form or otherdiscontinuous shape depending upon the location of the various recordingand pick-up coils.

A recording amplifier is provided for each recording coil and isprovided with two input leads designated X and 0. These amplifiers arenormally biased so that substantially no current flows in the recordingcoil windings. When it is desired to record an X signal a high positivevoltage with respect to ground is applied to the X input lead and whenit is desired to record an signal a high positive voltage with respectto ground is applied to the 0 input lead.

A pick-up or reading amplifier is also provided for each pick-up coil.The pick-up or reading amplifiers have two ouput leads or terminals, onedesignated X and the other 0-. In the exemplary embodiment of thisinvention described in detail herein, when O signals pass under thepole-pieces of the pick-up coil connected to the respective amplifiers,a low positive voltage is applied to the X output leads or terminals anda high positive voltage is applied to the 0 output terminals. When an Xsignal passes under the pole tips of a pick-up coil, a high positivevoltage is applied to the X output terminal of the pick-up amplifierindividual to said coil and a low positive voltage is applied to the 0output terminal by the respective pick-up amplifier.

In addition to the pick-up and recording coils located adjacent themagnetic drum described above, additional pick-up coils such as 50 andare provided for generating timing and synchronizing pulses. As shown inthe drawing these coils are located adjacent the periphery of the timingwheel [0| which is shown to be in the form of a gear wheel. Coil 50 isadjacent the wheel having a plurality of substantially uniform spacedteeth or poles While coil 5| is adjacent the timing wheel I02 having asingle gear tooth or pole. Each of the teeth or poles of the wheeladjacent coil 50 generates a pulse which is employed to control therecording of signals in the drum as will be described hereinafter.During each revolution a single pulse is generated in coil 5| which isused to restore numerous circuits to their initial condition so thesecircuits may start from a given initial-condition once during eachrevolution. Consequently, erors in the circuits will not be additive formore than one revolution of the drum. While special coils 5n and 5| areshown adjacent the gear or tooth wheels for generating timing purposes,it is also within the scope of this invention to provide the timingpulses from pickup coils such as 50 and 5! located adjacent channels onthe magnetic drum which channels will have the synchronizing pulsesrecorded in them in any suitable manner such as by an oscillator orcontinuous pulse generator or the like. However, in the exemplaryembodiment set forth herein the timing pulses are generated by means ofthe tooth wheels which are mounted upon the same shaft or at leastdriven at the same speed as the magnetic drum and usually from the samemotor or other driving means. The output of coils 50 and 5| is amplifiedby the respective amplifiers 60 and SI. Output coil 50 and amplifier B0are so designed that a high positive output pulse is ob-- tained foreach tooth of the gear wheel which passes under the pole-pieces of coilSt. The amplifier 61 contains the necessary pulse forming, pulse shapingmeans and means for otherwise controlling pulse characteristics as required. In an exemplary embodiment of this invention, pulse output fromamplifier 60 for each of the teeth of the gear wheel under coil 50 has aduration of approximately one-tenth the time required for a cell of themagnetic surface of the drum as defined above to pass under a pick-upcoil. This pulse duration is not critical and satisfactory results maybe obtained with pulses of such a duration.

Th output from amplifier 6! comprises a pulse of high negative voltageor polarity for each revolution of the drum or the single tooth wheel.This pulse has a duration which is appreciably greater than the durationof the timing pulses obtained from amplifier 60 but still shorter thanthe time required for a cell to pass under a recording or pick-up head.

The signals to be recorded will comprise either one or the other of thetwo diiferent signaling conditions such as voltage or potentialconditions across the line resistor, depending upon whether the line isopened or closed as will be described. One of these signaling conditionsis called an X signal herein and the other of these signaling conditionsis called an 0 signal. These two different signaling conditions, i. e.,X signals and O signals are represented by different currents orvoltages or different voltage conditions or different current conditionsin different circuits, conductors and terminals in the system. These Xsignals may also be represented by different magnetic conditions inparts of the equipment. These signaling conditions most frequentlycornprise a voltage or current of one polarity, i. e., positive ornegative, of relatively high, large, or maximum magnitude and a voltageor current of the same polarity but of relatively low or minimummagnitude. When desirable these signaling rents or voltages of the samedrum as it passes between coils when this portion of the drur may berepresented by other voltages such as by positive and negative curordifferent magnitudes, or by current and no current, i. e., a current ofsubstantially zero magnitude, or by a voltage and no voltage, etc.

The operation of the system may be better understood and. the initialoperation of the system improved, if it is assumed that the drum isinitially magnetized by applying a substantially continuous current toeach of the recording coils of the main recording drum or sectionsubstantially saturating the magnetic material in the the pole-pieces ofeach of the recording coils in one of the magnetic conditions caused byone of the two different types of signals or voltage conditions to berecorded in the drum. Thus it is assumed that this voltage will be inthe same direction as produced by the conditions or currents so-called 0signal when it is desired to record such a signal in the drum. Ofcourse, the opposite or X signal will then comprise magnetizing the drumin the reverse direction between the pole-pieces. In some instances, itis .rable to provide a third type of magnetization produce no voltage inthe pick-up or r Such a magnetic condition is readily obtained byorienting an additional coil adjacent to the s 3 channel and rotatingthe pole-pieces with spect to the channel so that they are 90 degreesdisplaced from the pole-pieces oi" the recordi g coil and thecorresponding piclr up coil. Thus an O is recorded in the magneticmaterial by orienting the so-called magnetic vectors in one tion, whichdirection causes a volt polarity to be obtained from the pi the poletips. The recording of an A srgna apply a reverse ma netization to themagnetic material and t the mag thus in effect will Oll netic vectors ina direction substantially degrees from the first direction and thuscause a voltage of the opposite polarity in the pick-up coil. lheerasing or third magnetic condition will cause the magnetic vectors tobe rotated at an angle of 90 degrees to the first direction and thuscause no voltage to be induced in the output of the pick-up coil.

When only two magnetic conditions are required then the first or zerocondition in general does not cause a voltage to be inducted in thepick-up coil, whereas the opposite magnetic condition representing an Xsignal causes a voltage of a predetermined polarity and wave shape to beinduced in the corresponding pick-up coil. It should be noted that thepick-up coils, recording coils and all of the control equipmenttherefore together with the electrostatic distributor or scanningmechanisms in accordance with this invention are common to all of thelines assigned to the slots on a given magnetic drum. The variouselemental areas on this drum called cells, however, are individuallyassigned to diiierent ones of these lines and at all times during thecall accurately record the electrical condition and the history of theelectrical condition of that line. The cells or slots or elemental areasassigned to a given line are employed for recording the condition ofonly that line and are never employed to record the condition of any ofthe other lines individual to the drum.

Considering now the operation of the system and referring moreparticularly to Fig. 1, two lines l4 and I5 are shown in detail and eachis provided with a calling switch such as H) and H,

respectively, anddials 20 and 2| or other suitable signaling devices.These lines may be of different lengths from short lines to long lineswhich may extend over considerable distances as in the case or"telephone subscribers lines, annunciator lines, etc. Each line isconnected to a ground and a source of electrical energy through resistorelements as shown in the drawing. For example, the upper conductor ofline I4 is connected to ground through. resistor l6 and the lowerconductor connected to battery through resistor is and similar resistorsl1 and i9 are shown connected to line i5.

So long as the calling switches i0 and I I remain open the voltage dropsacross resistors l6 and I! remain substantially zero with the resultthat the voltages applied to segments 32 and 33 of the electrostaticdistributor remain at substantially battery potential. However, when thecontacts ill close, current flows over line H and through resistors Itand I8 and causes a voltage drop to appear across resistor is with theresult that a more positive voltage is applied to the distributorsegment Consequently, a more positive voltage is induced in the scanningelectrode 255 when it passes a segment 32 which more positive voltage isapplied to the control grid of the cathode follower 2 i. In the specificarrangement shown in the drawing the same battery voltage is connectedto the shielding segments 30 as is connected. to the line circuits, 1.e., resistors 18, ill, etc. Consequently as long as the lines are idleno change voltage is induced upon the rotating member Substantially thesame results may be obtained by connecting the shielding segments 30 toground and connecting the line segments to resistors IE, it, etc. Inthis case the polarity of the output pulse will be reversed from thatdescribed herein so amplifier 2i; will include means for reversing theoutput polarity so a high positive pulse is obtained each time the lineis scanned, sampled, or tested when the line is closed and a low pulsewhen the line is open.

Furthermore, by connecting ground to the shielding segments 30 and theline segments to resistors i8, i9, etc., or by connecting battery tosegments 3d and the line segments to resistors 16, ll, etc., pulses ofrelatively large magnitude of one or the other polarity may be obtainedon member 25 when the line is idle and pulses of low or zero magnitudewhen the line is closed or busy. These pulses will then be inverted inamplifier 20 in any suitable manner so that a pulse of high positivevoltage is obtained from this amplifier when the line is closed and apulse of low magnitude or zero when the line is open.

Cathode-follower tube 2! is employed as an impedance-changing device todrive the main amplifier 20 and also to apply a voltage to the shieldmember 25 and the outer conductor or shield of the line connecting theamplifier to the stationary ring 24 which voltage is similar to thevoltage induced upon arm 25 and applied over the center conductor ofline 22 and through the coupling condenser or rings 23 to the grid oftube 2!. The application of the output of tube 2| to the screen orshield 22 causes the impedance of the scanning conductor to be raisedand causes its equivalent capacity to ground and other elements to begreatly reduced with the result that a greater voltage change is inducedin the scanning electrode 25 for a given voltage applied to the scanningline segments 32, 33, etc.

The signals are then amplified, shaped by the amplifier and when dried,20 which may comprise the gate circuit Zlli 24s of the gate circuit 2.collector element passes over a segment individual to a given line theoutput For convenience in referring to these direc tions ofmagnetization the left-hand coil of head III, for example, as shown inthe drawing is asproduce a direction of magnetization in the elementalareas of the surface of the drum called an signal. It is to beunderstood, however,

may be wound upon both of the pole-pieces of the recording head Ill. Asshown in the drawing the coils of the recording head I are connected tothe leads, one designated X and the other 0. Both of these leads arenormally maintained at a relatively low voltage near ground potential bythe gate circuit 2m. These input leads connect to terminals 2 and 3 ofamplifier I In which are coupled through condensers to the grids of the3l2 as shown in Fig. 2. In the exemplary embodiment the input grids ofthe amplifier tubes 3 and 3m are normally maintained or biased at anegative voltage with respect to ground output current flows in the poletips of coil Ill Gate circuits such are not changed.

as G! comprise a plurality of rectifiers or diodes which may be of thegermanium crystal type, or other suitable forms of crystals orcombinations of crystals or high vacuum diodes. The gate circuits havean input circuit shown at the bottom of the rectangle such as 2m whichis connected to the output of the synchronizing amplifier 68].

which in turn are connected to the rectifiers 2% and 208. This gatecircuit also has an input lead shown at the right-hand side of therectangle in turn nected to the rectifier element 201.

plary system described herein in detail the gate circuits are arrangedto have their input circuits or terminals connected to relatively lowsay about 25 volts or less thereto.

the drum passing under the So long as a low positive voltage is appliedto any one or more of the inputs current flows from battery 200, andfrom any of the other inputs having a high positive voltage applied toit, through the diode connected to the relatively low positive voltagewith the result that the common point which comprises an output from thegate circuit is maintained at or near the voltage of the relatively lowvoltage applied to that input lead or leads.

voltage to the A. input lead to amplifier H0 in response to a highpositive synchronizing pulse supplied from the synchronizing amplifierso to the common point between the diodes 294 and of the drum 0 inputlead to amplifier HE] when a high positive synchronizing pulse isapplied from the synchronizing amplifier iii] to the common pointbetween the diodes 204 and 205 with the result that an O is recorded inthe magnetic element of the drum passing under the recording head H! atthis time.

The gate circuits such as GI rectangle till may different manners.

shown within the be arranged in a plurality of These gate circuits maybe high positive voltage applied nizing lead. Such called OR gatecircuits, that is, circuits in which outputs appear in response to ahigh positive voltage applied to any one or more of the of a group ofthe input leads before a high positive voltage is repeated to thecorresponding output lead. Such circuits are frequently called ANDcircuits. Such circuits are obtained by applying suitable potentials tothe diode elements and properly orienting the diode element. Thesemitting one, as described above.

For example, with respect to the gate circuit Gl, it is necessary for ahigh positive voltage to be applied to the right-hand terminal of thedithe recording coil i H in response to a high positive synchronizingpulse from the synchronizing amplifier 60.

With respect to the inputs required to cause gate G! must be a highpositive voltage. However, in the absence of a recorder X signal passingunder the pick-up coil H5 at this time the output from the X lead fromamplifier H6 is a low positive voltage and the output from the 0 lead ofamplifier I I6 is a high positive as will be described hereinafter withthe result that a high positive voltage is applied to the diode 206.Consequently, when the voltage of the scanning electrode 25 becomes morepositive, a high positive potential is applied to the left-hand terminalof the diode 208 and as a result when the synchronizing pulse from theamplifier 60 is applied to the gate GI, the voltage of the X input leadto amplifier I I becomes a high positive voltage and causes an X to berecorded in the corresponding cell under the recording head I I I atthis time. No high positive voltage is applied to the 0 input lead toamplifier I III at this time. Then the arm 25 will move on to the nextsegment or terminal of the distributor or scanner. In case the next lineis also busy or has current flowing over it, an X will be written orrecorded in the next cell. Conversely, if the next line has no currentflow ing in it at this time, an X will not be written or recorded in thesucceeding cell because electrode 25 will be sufficiently negative andthus will not cause the application of a high positive voltage to theleft-hand terminal of diode 208.

After the above-described X is written in the cell corresponding to lineI4, in the manner described above, this cell will pass around the drumand pass under the pick-up coil or reading head H2 and cause an outputvoltage to be developed in the winding of this head or coil. The outputcoils from the pick-up head I I2 are connected to transfer amplifier II3 which causes the corresponding X to be recorded by the recording headH4 in the cell passing under this recording coil at this time. The Xrecorded by the recording 1 head III then continues around the drum andpasses under the erasing head H8. The erasing head comprises a permanentmagnet or a continuously energized electromagnet oriented in suchdirection that the magnetization of the drum after passing under thishead produces no output voltage in any of the pick-up coils under whichthis portion of the drum will pass. During the time the X recorded bythe recording head I II is rotating from the pick-up head I I2 to theerasing head H8 and then on to the recording head II I again, the Xrecorded by the recording head I I4 is also rotated around the drum sothat at approximately the same time that the pick-up arm 25 again passesopposite segment 32 connected to line It in the manner described above,the X recorded in the cell assigned to line I l on the drum in thechannel associated with head H5 will pass under head H5. As a result thevoltage induced in the pick-up head I I5 and amplified by amplifier H6causes a high positive voltage to be applied to the output X lead ofamplifier H6 and causes a low positive voltage to be applied over theoutput 0 lead from amplifier I IE to the left-hand terminal of diode 206at this time, so that when this next high positive pulse from thescanning mechanism due to the scanning of line I4 and the nextcorresponding high positive synchronizing pulse from the amplifier 60are applied to diodes 208 and 204 and 205, the voltage of the X lead isprevented from becoming positive. Consequently, no further signals willbe recorded by the head III at this time so no further voltages will beinduced in the pickup head I I2 by the cell in the channel under headIII assigned t However, the X recorded in the cell in the channel underheads I I I and H5 assigned to line I4 will remain until removed orchanged in the manner described hereinafter.

1 recording head I265.

The output voltage from amplifier is also applied to the left-hand inputterminal of the gate G2 shown within rectangle 2H in Fig. 1. This gateis in turn connected through an amplirrer iii! to a recording head Iwhich ampliher and recording head are arranged to write or record onlyXs upon the corresponding channel of the drum. Thus, each time thesynchronizing pulse from the amplifier is applied to the diode 2%, ahigh positive pulse appears on the X lead from gate "all when positivevoltage is also applied to the diode 2I6 from the scanner amplifier Aspointed out above, such a high positive voltage is received fromamplifier 20 and thus applied to the diode 2 It each time thedistributor or scanner arm 25 passing adjacent the segment of a lineover which line current is flowing with the result that an X is writtenin each of the cells in the channel under the recording head i2Iassigned to the respective lines having current flowing over them. Whenthese cells pass under the pick-up head I22, they induce voltagestherein which are repeated by the repeating or transfer circuit I23 tothe recording head ltd which records corresponding Xs in thecorresponding cells in this channel assigned to the respective lines.

Returning now to the X recorded in the cell assig. ed to line I in thechannel under the head as the drum rotates this cell passes from underthe head I22 to the erasing head I28. At this time this X is erased andthe cell then continues to travel around the drum and again passes underthe recording head IZI where an X is again written in this cell ifcurrent is still flowing in. the line at this time. As pointed outabove, the collector arm 25 will again pass adjacent to segment 32 atthis time.

Consider now the X written or recorded by the As the drum rotates, thisX will pass under the reading or pick-up head E25 and cause an output inthe output amplifier lift indicating that an X was recorded in thecorresponding cell in a channel under the recording head ti t. As thiscell or area continues to rotate, it will pass under the erasing headI29 which changes the magnetization of this cell so that it is no longercapable of inducing any voltage in the pick-up head tilt. However, aspointed out above, if current continues to iiow in the line so that an Xis again written or recorded by head I2I, the corresponding voltage willagain be induced in the pick-up head I22 and transferred to therecording head In and recorded in the same cell assigned to line I4. Theabove operations then continue for each or the lines so long as linecurrent flows over the line. At this time it should be noted that thechannel under the heads III and H2 does not have either an X or an 0recorded in them; the previous recordings having been erased. Thechannel under the heads IZI and I22 has an X written or recorded in eachof the cells each time these cells pass under recording head I2I so longas the corresponding line has current flowing in it. The X signalswritten in this channel are continually transferred to the recordinghead I24 and then later erased by the erasing head H8. X signalsrecorded by the recording head I24 in turn induce output voltages in thepick-up head I25 and then are erased by the erasing head I29 associatedwith the channel of heads I24 and I25.

The above-described operation of the various heads, coils, circuits,amplifiers, gates and scanning mechanism has been described with referina predetermined cell or unit area on the surface of the magnetic drumassigned to the respective lines.

nals will be recorded by recording coil I RI of the delay portion of thedrum at the X output leads and low voltages exist at leads fromamplifiers H6 and I29 due to the Xs recorded in the cells or elementalareas of the drum up coils H and I25.

In response to an opening contacts of the dial wise the potential dropof the line by the or contacts It or otherand as the rotating elementagain passes segof amplifier 25 becomes more negative. As a result an Xwill not be revoltage pulse transmitted over the X lead from amplifierH6. The outputs of amplifiers lit, I26 and I36 are connected to atranslating or combining circuit 25L The combining circuit 25I comprisesa plurality of two-element diodes which may be of a high vacuum type butas in dicated in the drawing, these elements may also comprise crystalrectifiers of any suitable type including germanium and other types ofrectifying contacts, semiconductors and the like.

from amplifier H6. The XO lead also has a rectifier connected between itand the 0 lead from amplifier I 26. These rectifiers are poled in such adirection that the voltage on the X6 lead is at a low value so long asthe voltage onthe X lead from amplifier Ht or sponding rectifier willconduct appreciable current from the battery 252 and thus maintain avoltage of the X0 lead at a relatively low value near the lowest valuevoltage applied to either X lead from amplifier I I6 or the 0 lead fromamplifier I26 whichever of these two leads is the lowest in voltage.

However, when an X passes under the pick-up coil IE5 and an 0 passesunder the pick-up coil I25 substantially simultaneously therewith,posiamplifier I26.

Due to the previous magnetization of the other portions of the drum theoutput from the amplifier I36 will be a high positive voltage on theassigned to the line I4.

As a result a high positive output voltage ap-.

pears on lead X00 at this time. The X00 lead has a rectifier or diodeconnected between it and the X output lead from amplifier I I6 and adiode it and the 0 output lead from amplifier I26 and a diode connectedbetween it and the 0 output lead from amplifier I35. rectifiers arepoled in such a age of any of the above-identified leads from theamplifiers II l, I26, I35 is a low positive voltage. However, asdescribed above, the first time after line It has been opened and theslot assigned to this line passes under the pick-up coils H5,

I25 and I35, a high positive voltage appears on the output leads fromamplifiers HIS, I 36 connected to lead X00 through the diodes asdescribed above. Consequently the voltage on lead X00 becomes high atthis time. At the same time another cell or elemental area of thesurface of the drum or cylinder assigned to line It passes under therecording coil I3I. The high positive voltage on lead XOO which isconnected to the diode 222 in the gate circuit 22I causes a highpositive voltage to be repeated on the X plied to the output X lead fromamplifier I 36 to become high. As a result positive voltage does notagain appear on the X00 lead because the output voltage of the 0 leadfrom amplifier I36 is now low and thus controls the voltage of the X00lead.

After the X recorded by the passes under recording coil I 3| I32 and istrans- I34 as described mains recorded in the elemental area assigned toline It associated with the pick-up coil I35 until changed as will bedescribed hereinafter.

So long as line It remains open no further signals are recorded by anyof the recording coils or I24 with the result that high :positivevoltage appears on lead X each time the arm passes segment 32 and thuseach time the X originally recorded by the coil II4 passes under thepick-up coil H in the manner described These high positive voltages aretransmitted to a counting or timing circuit and employed to indicate adisconnect or termination of the call in a manner to be describedhereinafter.

However, assume that before any disconnect or termination signal isrecognized due to the or timing circuit ii, the voltage of the armbecomes more positive when it next passes segment As a result an Xsignal will be recorded. by the recording coil I2I in the delay sectionof the magnetic drum. At a short interval of time X signal will berecorded by the recording coil I24 in the cell or elemental areathereunder assigned to line M in a manner described hereinbefore. Whenthis portion of the drum passes under pick-up coil I25 the X signaloriginally recorded by the recording coil II4 also passes under thepick-up coil II5 with the result that high positive voltage appears onthe X output leads from amplifiers lit and IE9 and a low voltage isobtained from the 0 output leads from these amplifiers.

The XXX lead from the translating or comlbining circuit 25I has a diodeconnected between it and the X output leads from each of the amplifiersIIB, I26 and I35 with the result that a high positive voltage isobtained from this lead the first time the X originally recorded by therecording coil H4 and the X recorded by the coil I24 and the X recordedby recording coil I34 pass under the pick-up heads H5, I25 and I35 afterthe line I4 has reclosed.

Lead XXX extends to the diode 223 or the gate or translating circuit 22Iand also to the diode 232 or the gate circuit 23L The high positivepulse applied to the diode 223 at this time causes area of the drumassigned to line I4 under the coil I3! at this time. Likewise, a highpositive voltage on lead XXX at this time applied to the diode 232causes an X signal to be recorded by the recording coil Illi which Xsignal is later transferred to the recording coil Hi4 and recorded inanother cell or elemental area or the drum under coil I44 which islikewise assigned to line I4.

The 0 signal recorded in the I3I later passes under the pick-up coil I32and is transferred to the recording coil I34. At the time this 0 signalis applied to the recording coil I34 the X signal previously recorded inthe cell which is now under this coil and assigned to line I4, will bewritten over or changed to an 0 signal and thus in effect canceled andan 0 signal substituted therefor. Thus after the elemental areasassigned to line I4, pass under the coils II4, I24, I34 and I44 therewill be X, X, 0 and X signals respectively stored or recorded in them.

Thus in response to the closure of a calling line such as I4, an Xsignal is recorded by coils III and H4 in the cells or elemental areasassigned to said line I4. These areas are in the channel designated GI.In response to the subsequent opening of the calling line I4 an Xsignal. is recorded by coils [3i and I34 in the areas assigned to lineI4. These areas are in the channel designated l-I herein. In response tothe subsequent reclosing of the calling line I4 an X signal cell undercoil is recorded in the elemental areas or cells under coils MI and I44assigned to line I4. These areas are in the channel on the magnetic drumdesignated channel J herein.

Any of the above signals or sequences of signals, i. e., the closure ofa calling line, the closure of the calling line followed by the openingthere of, or the closure of the calling line followed by an opening ofthat line which opening is followed by a reclosure or the line, maycomprise a calling signal and the exemplary embodiment described indetail herein may be arranged to recognize and respond to any or all ofthe above calling signals or to more complicated patterns of signals asdescribed hereinafter. As shown in Fig. 1 the input lead M0 to theregister and display apparatus is connected to the X output lead fromamplifier I45 of channel J. Consequently, this equipment responds to thelast type or call signals enumerated above. However, by connecting alead similar to I48 to the X output lead from the amplifiers of otherchannels, such as GI or H, instead of from channel J the system willrespond to the other call signals described above. When desiredadditional register and display equipment may be provided and connectedto different ones of the channels for responding to different types ofcall signals.

In order to display the call it is necessary that the display orregistering mechanism be idle and properly reset to a zero condition.This registering equipment as shown in Fig. 1 comprises a plurality ofcounter tubes IOII, IOI2, etc., reset inuitivibrator tube I050, a groupof registering tubes i040, w ll, etc., indicating tubes I010, I01I,etc., and reset tubes I0ii0, IOBl, etc. A control and combining circuitcomprising the diodes I53, led, and Hill together with a repeatingcathode follower tube BII is provided for controlling the registeringequipment. The restoring multivibrator tube I050 is arranged so that theconduction within the tubes automatically returns to the normalconditions after a restoring or reset operation. The circuit ofmultivibrator tube I050 is arranged so that with key I05I unoperated,

e as shown in the drawing, the left-hand section will be conducting andthe right-hand section non-conducting due to the connection of the gridof the left-hand section to a more positive bias voltage than thatapplied to the grid of the righthand section. Under these circumstancesthe voltage of the anode of the left-hand section is at a relatively lowvalue so that the right-hand sections of gates 13%, 732, etc. areblocked at this time. The voltage of the anode of the righthand sectionof tube I050 is at its most positive value when the right-hand sectionis conducting substantially no current. As a result, the positivevoltage is applied to the upper terminal of diode I54, which volage isin such a direction that it produces substantially no current flowthrough the diode because it is in a reverse direction to the mode ofeasy conduction of the diode.

The counter tubes Hill and IOI 2 comprise two representative stages of amultistage binary counter employed to designate the line over which thecalling signal or signals originate. On the binary number system eachplace or denominational order of a number has either one or twodifferent digits, i. e., a one or a zero. The tubes till I, liiIil,etc., represent each stage or denominational order and conduction ofcurrent by one section of such a tube represents a zero for that stageor denominational order and the other section conducting represents aone for that de- These counter stages are arranged to be reset once perrevolution of the drum be described hereinafter. Thereafter they counteach of the synchronizing Pulses which define the unit areas individualto the respective lines. In the exemplary embodiment of the presentinvention a synchronizing pulse is generated for and defines each of theelemental areas under the picleup coils assigned to the individualcalling lines and these ele mental areas assigned a line are under thevari-- ous pick-up coils as described above when the arm passes thesegment connected to that line. Consequently, the condition of thecounter tubes IBM, I012, etc., accurately identifies the line havingelemental areas under the various pick-up coils at each instant of time.

As shown in the drawing the counter tubes nominational order.

I OH and H312 have been arranged so that they are reset to their zero orinitial condition once per revolution by a negative pulse applied tothem as will be described hereinafter.

left-hand section of these tubes.

The synchronizing or timing pulses after passing through the delay line29| and the repeating and inverting tube 298 are applied to both secwillbe at a lower voltage than the left-hand section. Consequently, thediode connected to this right-hand section will oiTer appreciably moreimpedance to the pulse than will the diode connected to the left-handsection.

anode of the section of tube it! i flows through the left-hand sectionbut not through the right-hand section until the next timing pulse isapplied to both sections of this tube.

The second delay timing negative pulse is again applied to both anodesof tube Hill in the same manner as above described. At this time,however, current flowing through the left-hand hand section which causescurrent to start to flow through this section.

Thus, upon the application of each of the delayed negative timing pulsesthe conducting conditions in tube mu are reversed.

The initiation of a discharge through the right-hand section of tube umcauses the voltage of the anode of this section to fall fromsubstantially the fullanode battery supply voltage to a much lowervoltage which in turn applies a negative pulse through the couplingcondenser and the rectifiers or diodes connected to the two anodes oftube ifll2. Under the assumed conditions, prior to the application ofthis negative pulse, the right-hand section of tube IGIZ is conductingcurrent while the left-hand section is not. The application of thenegative pulse to the two diodes does not at once efifect the cutoff ofthe right-hand section. However, the application of the negative pulsethrough the diode connected to the anode of the left-hand section andthen through the coupling arrangement to the control grid of theright-hand section reduces or interrupts the current flowing to theright-hand section of this tube thus causing the anode of this sectionto rise in voltage and apply a positive voltage to the grid of theleft-hand section which then starts to conduct current and applies astill more negative voltage to the grid of the right-hand section. Inthis manner the application of the negative pulse through the couplingcondenser and coupling diodes causes the current flowing through theright-hand section to be interrupted and a flow of current from theleft-hand section initiated.

Had the left-hand section been conducting current instead of theright-hand, then the ap plication of the negative pulse would betransmitted through the opposite diode and cause the interruption of thecurrent flowing through the left-hand section and an initiation ofcurrent flowing through the right-hand section. In other words, upon theapplication of each negative pulse from the anode of the right-handsection of tube I0! I, the discharge current within the tube H2 istransferred from the previously conducting section to the other section.In a similar manner, each time the anode of the righthand sectionbecomes more negative due to the initiation of a flow of current to thissection of tube IBIZ, a negative pulse is relayed to the next counterstage and so on.

With the right-hand section of tube I!!! I conducting and the left-handsection of tube I012 conducting, these two tubes indicate a count of 2,since two synchronizing pulses have been applied to the cathodes of tubeiilll as described above.

It should be noted that the counter tubes are advanced by delayed timingpulses. In other words, these counter tubes are not advanced until theundelayed timing pulses have controlled the gate circuits 73!, in amanner described hereinafter. Consequently,

the timing pulses tubes in .a 'manner the counter tubes are advanced bythe respectwhen necessary. "ducting conditions of the counter tubes ofI011,

high postiive potential. However,

that the voltage of '19 control the gate "circuits and accuratelyindicate the setting of the counter described "hereinafter before tivegdelayed timing pulses.

In a similar manner additional synchronizing pulses are counted bytubesIOII, II2 and similar in the drawing but provided. Thus the setting ofthe contubes not shown I012, etc., at all times accurately representsthe identity of the callingiine being tested or scanned. at each instantof time.

'Tubes I040 and I041 are'gas-filled tubes having a gaspressureofairaction of an atmosphere and in which the control grid loses controlof the current flowing in the anode cathode circuits once this currentstartsto flow. These tubes are initially set or conditionedwith nocurrent fiowing :in their anode-cathode circuits-and are restored tothis condition after each call has been recorded and noted as will'bedescribed hereinafter. With each of the tubes 1040, I041, etc.non-conducting their anodes are at a relatively the diodes I55, I;56,etc., are connected to the-respective'anodes of tubes I040 and 'I'04I1inthe directionto oppose the flow of current throughthese diodes whenthese tubes are nonconducting. However at this time the commonterminalof the combining circuit which is connected to the grid of tube9II is maintained at a relatively low voltage by the output of amplifierI46 until an X signal recorded in channel J .is picked up by thecorresponding pick-upcoil I45.

Upon the sampling of line -I4 during the next revolution of the drum I04after the Xsignal is recorded in channel J of the delay section of .thedrum .the output of the X lead of amplifier I46 will have a highpositive voltage applied to its X lead due to the X signal recorded inthis channel of the magnetic drum.

Under the assumed conditionsthe high positive voltage on the X lead I48from-amplifier I 4'5 is the last high positive voltage to be applied tothe diodes I53, I54, .I55 and I56 with the result the common conductorof this combining circuitchanges to a high positive value and tube HI Irepeats ahigh-positive voltage in its output or cathode circuit todiodes of the gate circuits I3I, 132, etc. If the corresponding countertube indicates a l, the right-hand sections will be non-conducting:andthus have their anodes at a relatively high voltage. If, on the otherhand, these 'countertubes indicatea count of zero the right-hand sectionwill be conducting and its anode at a correspondingly low voltage withthe result that the left-hand sections of gates I3I and 132 aresubstantially 'blocked'or ineffective to transmit a positive voltage totheir common or output terminals.

Thus, during the time the X signal recorded in channel J passes underthe pick-up coil I45 and causes a high positive voltage to be applied tothe output lead I40 from-amplifier I46, positive voltage will be appliedto all of the input terminals on the left-hand side of the gate circuitsI3I, 132, etc., when the synchronizing pulse occurring at this time isreceived from the pickup coil 50 and amplifier 60. As a result, thetubes I040, I04I, etc., which are individual to the counter tubes IOI I,'IOI2, etc., which indicate a count or digit value of 1 have a positivevoltage applied to their control grids. The tubes I040 and -I0-4Iindividual to counter tubes IOII,"IOI2,

in the cathode circuits of tubes have discharges initiated through themat subthrough the register etc., which are in their original or initialcondition, that is, indicating a digit value of zero, do not have apositive voltage applied to their control grids. Consequently,discharges are initiated through the register tubes I040, I04I, etc., atthis time if a corresponding counter tube is in its operated conditionand not initiated if the corresponding counter tube is in itsinitial-orzero condition. As a result, the register tubes I040, I04I,etc., have discharges initiated through them in accordance with thecount of the binary counter tubes IOI I, IOI2, etc. In addition, highpositive pulse from amplifier causes the counter to'advance by a countof one. Thus the count of the binary counter designates or identifreethe calling line which is assumed to be the line designated I4 in thedrawing.

Generally the count of the binary counter which identifies therespective calling lines will not be the directory number of the callingline but may be such number or represent such number when desired.

Indicating devices I010 and IB'II are connected I040 and I04! andstantially the same time discharges are initiated in the correspondingregister tubes I040 and WM, thus indicating to an attendant the identityof the calling line. It is to be understood of course that relays,switches or other indicatorsor other types of mechanisms may be employedin addition to or in place of the gas tube indicators I010, I01 I, etc.,for indicating the identity of the calling line or for responding to thecall from the calling line inany desired manner. These responsivedevices mayactuate other switching devices, signals, ,buzzers, lamps andthe like.

In addition, the initiation of a discharge tubes I040, I041, etc.,causes the anode of the tubes through which discharge is initiated tofall to a relatively low voltage with the result that the voltageapplied to the diodes I55, I56, etc., also falls to a relatively lowvalue. Consequently, the voltage applied to the grid of tube 9II alsofalls to this low value so that the output of tube 9 LI is no longersufiicient to permit positive voltages to be transmitted through thegate circuits .I3I, 132, etc., and .as a result the register circuitswill remain in the condition indicating the identity of a calling lineuntil restored by an attendant or by other means.

When it is desired to restore the register circuits described above totheir initial or zero condition. key I05I will be operated which appliesa more negative voltage to the grid of the lefthand section of tube I050for a short interval of time during the charging time of the smallcondenser I052. As a result of the cross couplings of the monostablecircuits of tube I050 the current flowing through this section isinterrupted and current flow through the right-hand section of this tubeinitiated. .As a result, the voltage ther signals or high positivepulses received over conductor I48 cannot be relayed to the grid of tube9I I, even if and when the other input controls described herein wouldotherwise permit pulses to be repeated from conductor I48 to the grid oftube 9| I. In addition, the voltage of the left-hand anode of tube I050becomes morepositive and is applied through the right-hand terminals ofgates'13I, 132, etc. As a result, positivt voltage is applied to thegrid of the restoring tubes I060, I06I, etc., during the application -o:

restored to normal,

21 synchronizin pulses to the gate circuits I3I. 132, etc.

The application of positive voltages to the control elements of tubesI86?) and ltti causes these tubes to conduct current with the resultthat the voltage of their anodes and the anodes of the register tubes IIlitI, etc., is reduced to a low value. The voltage of the cathodes ofthe register tubes is maintained at the voltage resulting from thedischarge current flowing through the cathode resistor by the condenserconnected around that resistor. The reduction of the anode voltage ofthese tubes H3650, mt I, etc, is sufficient to reduce the voltagebetween the anodes and cathodes of these tubes, below the sustainingvoltage required, by the register tubes to maintain a discharge throughthem. As a result, the discharge through these register tubes isinterrupted and the register circuit restored to normal. Likewise, theindicating tubes it'll} and iiili are also thus canceling the identityof the previous called line.

Thereafter, as condenser i052 continues to charge the voltage of thegrid of the left-hand section of tube i050 approaches the voltage of thegrid of the right-hand section. When these two grid voltages differ byless than the magnitude of the negative pulses as applied to thecathodes of both sections of tube ittitl the next delayed negativesynchronizing or timing pulse applied to the cathodes of this tubecauses the gridto-cathode voltage of the left-hand section to becomesufficiently positive to initiate a flow of current through theleft-hand section of tube I050 which in turn, due to the crossconnections between the sections of this tube, causes the currentflowing through the right-hand section to be interrupted. As a resultthe voltage of the anode of the left-hand section falls to a relativelylow value so that no further pulses are transmitted through theright-hand terminals of the gate circuits 13!, I32, etc. In addition,the voltage of the right-hand section of tube I050 rises so thatpositive voltage is applied to the diode ltd thus indicating that theregister circuit is again in condition for responding to other X signalsrecorded in channel J.

The X signals recorded in the various channels as described above may becanceled or removed by applying 0 signals to the corresponding recordingamplifiers in response to the opening of key Id of line M, for example,with the result that after a predetermined time of positive signals orpulses on the X0 lead at times assigned to line it for example, or aftera'predetermined number oi said signals have been received over thislead, the timer circuit 2*!0 functions and causes zeros to be written inall of the channels GI and J which may have Xs stored in them in theindividual areas assigned to the respective calling lines.

It is thus evident that the calling arrangement described is capable ofrecording a call originating on any one or more of a plurality of linesand then register and indicate this fact and the identity of the lineover which the calling signals originated. That portion of the equipmentrequired to indicate these signals may later be restored to normalwhereupon it is ready to register and indicate the signals received overthe next line the elemental. areas of which have a complete series ofsignals recorded in them and the pole tips of the pick- The identity ofthis line is also indicated' It is also evident that calls from all ofthe lines may all be substantially simultaneously recorded by themagnetic recording equipment and the associated electrostatic scanningor distributor mechanism.

When desired, the anode of the lefthand section of tube I050 or theoutput of the repeating tube all may be connected to the right-hand sideof gate circuit 2$I and cause a zero to be recorded in channel J in theelemental area of this channel assigned to line it, for example, withthe result that after the indication of a call has actuated the registercircuit and equipment the X in this elemental area of channel J will becanceled and changed to an 0 signal.

Details of the recording amplifiers, recording coils, pick-up coils,pick-up amplifiers and transfer amplifiers and equipment are shown inFig. 2. Here the two sections of the drum are illustrated as two drumswherein the delay drum or section of the drum is illustrated by drum ltdand the storage section by drum I 05. The recording amplifiers, such asII ii, are illustrated by tubes 3H and 3I2. These tubes may be separatetubes as shown in the drawing or they may be sections of a twin tube.The tube Si! is employed to write or record Xs in the elemental areas ofthe corresponding channel, while tube 3 I 2 is employed to write orrecord zeros. Thus, each time a positive pulse is applied to the No. 2terminal and thus through the coupling condenser to the grid of tube 351 current flows in the output or anodecathode circuit of this tube andthrough the X winding of the recording or Writing coil III, for example.Conversely, when a positive pulse is applied through the couplingcondenser to the No. 3 terminal positive voltage is applied to the gridof tube 3 I2 with the result that current flows in the output circuit oftube 352 and through the O winding of the recording coil l i I, causinga zero to be recorded in the elemental areas passunder this coil at thistime.

The elemental areas recorded by the recording coil I II then rotatepart-way around the delay drum I05 and pass under the for the wave formsillustrated by the small curves designated TX and T0 in response to an Xsignal or an 0' signal passing under the pick-up coil l I 2. Thesevoltages are applied through respective resistances to the grids oftubes i355 and EH13. As shown in the drawings, tube 3 l5 has a condenserconnected between its anode and grid which condenser in combination withsaid grid circuit re sistance causes the combined circuit to operate asan integrating device and in effect integrates the signal applied to thecontrol rid of this tube. Likewise, tube BIG has a condenser ZiIdsimilarly connected and integrates the voltage wave form applied to thecontrol element or grid of tube Slit with the result that the outputwave form of the anodes of these tubes is as illustrated by the curvesdesignated Eli-X and .iI'i O. It is to be understood that the tubes 355and represent a suitable ainplh ler which may comprise one or morestages of amplification, depending upon the extent of amplificationrequired and the accuracy of the integration necessary. The output ofthe integrating tubes 5H5 and 356 is connected to the control grids oftubes 322i and 322, respectively. These grids are also biased so that inthe absence of a signal applied to them substantially no current flowsin their output circuits. In addition, these grids are connected to asource of synchronizing signals received over lead 305 so that whenpositive synchronizing signals are lead 3&5 and the voltage from either316 is at a high positive value, current will fiow in the correspondingtube 3'Zl or 322 and cause a corresponding X or signal to be recorded inits elemental area under the recording coil H4 at this time.

Thereafter, the signal or signals are carried around the drum )5 andpass under the pole tips of the pick-up coil H5. The output of coil H5is applied to the integrating tube 33l and associated circuit andintegrated as before and then repeated by tube 332. The integratedsignal applied to the grid of tube 332 comprises a voltage of relativelyhigh amplitude in response to an X signal passing under the pole tips ofcoil H5 so a high positive voltage is repeated by the cathode of thistube to the X output lead. Conversely, when the integrated signalapplied to the input of tube 332 comprises a voltage of relatively lowamplitude response to an 0 signal passing under the pole tips of coilM5, the anode of tube 332 is at a high positive voltage in response tosuch O signals and this positive voltage is coupled through a gas orhigh vacuum diode 333 to the 0 output lead where it causes a highpositive voltage to be applied to this lead. These voltages are employedin the circuits as described herein to control the various otherrecording and indicating circuits. The change in voltage applied to the0 lead in response to an XI signal passing under pole tips and thechange in voltage app-lied to the X lead in res i156 an 0 signal passingunder the pole tip or" the picl-up coils are both of low magnitude.

After the signal recorded by the re Hi as described above passes it derthe pick-up or reading coil H2 it will pass under the eras-- ing coil iHi be erased in the manner described hereinbeiore whereupon theelemental as signed to the respective lines in ccridition to respond tosignals recorded by the recording coil l l I.

It should be noted that the pick-up coils as shown in Fig. l have theirpole-pieces oriented with respect to the cylinder such that the airgapextends circumi'erentially around the cylinder. Consequently,

the recording co1ls orient the iagnetic vectors circumierentially aroundthe cylinder in their respective channels. As shown in Fig. 2 theair-gap is shown extending along the axis or the drum and at rightangles to the arrangement shown in 1. The coil H8 has likewise beenshown rotated 90 degrees from that shown in 1. It is to be understoodthat the recording and pick-up coils as well as the other equipmentoperate with the coils in either orientation. However, in an exemplaryembodiment the coils have been actually oriented as shown in 1. Theair-gaps of the coils have been rotated through substantially 90 degreesin the showing in Fig. 2 to aid in the drawing and un derstanding of themanner in which the various coils are located one relative to anotherand the flow of signals or pulses from the first recording coil throughthe delay drum and then to the storage drum and finally to the finalpick-up coil from the storage drum. it is to be understood, of course,that when desired the coils may be arranged as actually shown in Fig. 2and as satisfactory operation will be obtained when the coils are soarranged.

Although a specific embodiment of the invention has been shown in thedrawing and described in detail herein, it will be understood thatvarious ill modifications may be made without departing from the scopeand spirit thereof as defined in the appended claims.

What is claimed is:

1. In combination, a capacitative commutator comprising a plurality or"fixed conductors insulatively supported from each other, anotherconductor, means for moving said other conductor into spacedrelationship successively with each of said fixed conductors to form anelectrical condenser therewith, an electrostatic shielding membersurrounding said other conductor and movable therewith for shieldingsaid other conductor from the electrical fields of all of said fixedconductors except the one with which said other conductor forms acondenser at each successive instant of time.

2. In combination, a capacitative commutator comprising a plurality offixed conductors insulatively supported from each other, anotherconductor adapted for movement into spaced relationship successivelywith each of said fixed conductors to form an electrical condensertherewith, a shield surrounding said other conductor and movabletherewith, electronic means controlled by the voltage of said otherconductor for maintaining said shield at substantially the same voltageas said other conductor.

3. A capacitative scanner comprising in combination a plurality of fixedconductors insulatively supported from each other, a rotatableconductor, means for rotating said rotatable conductor into spacedrelationship successively with each of said fixed conductors to form anelectrical condenser therewith, another fixed conductor supported inspaced relationship with said movable conductor and forming a condenserof substantially constant capacity therewith forming an electricalcoupling to said movable conductor.

4. A capacitative scanner comprising in combination a plurality of fixedconductors insulatively supported from each other, a rotatableconductor, means for rotating said rotatable conductors into spacedrelationship successively with each of said fixed conductors to form anelectrical condenser therewith, another fixed conductor supported inspaced relationship with said movable conductor and forming a condenserof substantially constant capacity therewith forming an electricalcoupling to said movable conductor, a shield member surrounding saidmovable member and movable therewith, a second fixed conductor supportedin spaced relationship with said shield member forming an electrostaticcapacity therewith for providing an electrical coupling to said shieldmember.

5. A capacitative scanner comprising in combination a plurality of fixedconductors insulatively supported from each other, a rotatable conductorrotatable into spaced relationship successively with each of said fixedconductors to form an electrical condenser therewith, another fixedconductor supported in spaced relationship with said movable conductorand forming a condenser of substantially constant capacity therewithforming an electrical coupling to said movable conductor, a shieldmember surrounding said movable member and movable therewith, a secondfixed conductor supported in spaced relationship with said shield memberforming an electrostatic capacity therewith for providing an electricalcoupling to said shield member, electronic repeating means controlled byvoltages 25 derived from said movable conductor for applying similarvoltages to said shield member.

6. In combination, a capacitative scanner comprising a plurality offixed conductors insulaperiphery of said cylinder and control means interconnected between said amplifier and said coils for changing themagnetic condition of said cylinder under control of the electricalcalling signals of said lines.

9. In combination, in a calling system, a plurality of calling lines,means for applying electrical calling signals to said lines; anelectrostatic distributor comprising a fixed electrically conductingsegment individually connected to each of said lines, a rotatablemember, and means relationship with each of said segments; cularcylinder of magnetic material, means for rotating said cylinder aboutits axis, a plurality of recording and pick-up coils adjacent the periphery of said cylinder; interconnections between said rotatable memberand said pick-up and recording coils for recording in the elementaladjacent said movable member at said same instant of time.

substantially recording coils located adjacent the periphery andadjacent a individual to said coils.

11. In combination a capacitative scanner comprising a plurality offixed conductors insulatively supported conductors.

12. In combination, a comprising a plurality capacitative commutator offixed conductors incessively into spaced relationship conductors.

13. In combination, a capacitative commutator comprising a plurality offixed conductors in- With said fixed member surrounding said movablecondenser and movable thereand said recording elements for recording thevoltage condition of successive ones of said fixed conductors insuccessive groups of said magnetic recording elements.

16. In combination, an electrical capacitative commutator comprising aplurality of insulatively supported fixed conductors, a movableconductor, means for moving said movable conductor into spacedrelationship successively'with each of said fixed conductors to form anelectrical condenser therewith, an electrostatic shielding membersurrounding said movable conductor and movable therewith for shieldingsaid movable conductor from fixed conductors preceding and succeedingthe fixed conductor with which said movable conductor forms anelectrical condenser at each succesive instant of time.

17. In combination, an electrical capacitative commutator comprising aplurality of insulatively supported fixed conductors, a movableconductor, means for moving said movable conductor into spacedrelationship successively with each of said fixed conductors to. form anelectrical condenser therewith, an electrostatic shielding membersurrounding said movable conductor and movable therewith for shieldingsaid movable conductor from the electrical field of a fixed conductoradjacent the fixed conductor with which said movable conductor forms anelectrical condenser at each successive instant of time.

18. In an electrical signal receiving system in combination, means forindividually terminating a plurality of electrical signaling lines, anelectrostatic scanner comprising a fixed conductor individual to thetermination of each of said lines interconnected with the respectiveones of said line terminations, means for applying the electricalsignals received by said line terminations to said fixed conductorindividual to the respective line terminations, a rotatable conductor,means for rotating said rotatable conductor into spaced relationshipwith each of said fixed conductors, an amplifier controlled by thepotential induced upon said rotatable conductor, a magnetic cylinder,apparatus for rotating said cylinder at the same speed as said rotatableelement, a plurality of recording and pick-up coils located adjacent theperiphery of said cylinder and con trol means interconnected betweensaid amplifier and said coils for changing the magnetic condition ofsaid cylinder under control of the electrical signals received by therespective ones of said line terminations.

19. In combination, in an electrical signaling, system, electrostaticdistributor comprising a plurality of fix ,d conducting segmentssupported insulatively from each other, means for applying; electricalsignals to said iixed conductors, a rotatable member, means for rotatingsaid member successively into spaced relationship with each of saidsegments, a circular cylinder of magnetic material, means for rotatingsaid cylinder about; its axis, a recording and pick-up coil adjacent tothe periphery of said cylinder, electrical interconnections between saidrotatable member and said pick-up and recording coil forconveying'signals from said rotatable member to said recording coils forrecording said signals in the elemental areas of said cylinder undersaid coil at substantially the same instants of time that said rotatablemember is in spaced relationship with respective ones of said fixedsegments.

20. In combination, an electrostatic capacitative commutator comprisinga plurality of fixed conductors insulatively supported from each other,a movable conductor, means for moving i said movable conductor intospaced relationship successively with each of said fixed conductorstoform an electrical condenser therewith, an output circuit, electricalrepeating means electrically interconnected between said movableconductor and said output circuit for repeating into said output circuitvoltages induced on said movable conductor.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,238,089 Wiklrenhauser Apr. 15,1941 2,257,894 Winsor Oct. 7,1941 2,281,495 Hammond Apr. 28, 1942 2,329,544 Larsen Sept. 14,19432,437,064 Andersen Mar. 2, 1948 2,587,780 Smits Mar. 4, 1952

